The present applicants provide a torque variation absorbing device comprising a driving member fixed to a drive shaft, a driven member arranged coaxially with the driving member and rotatably supported on the driving member, and torque limiting mechanism and a damping mechanism interposed between the driving member and the driven member.
In order to improve durability and to ensure good performance of the torque variation absorbing device, the following points are desired to be solved.
As a first point, a coil spring constituting a part of the damping mechanism should be prevented from being deformed excessively outwardly or inwardly and touching the members outside or inside of the coil spring in order to preserve durability and performance of the torque variation absorbing device.
As a second point, in order to absorb effectively vibration of an engine by a hysteresis mechanism, a damping mechanism and a torque limiting mechanism, it is important to determine appropriately a ratio of a moment of inertia of the driving member to that of the driven member as well as to determine specific values of each member. When the ratio is not set appropriately, the resonance point of the vibration absorbing device will be within the operating speed of an engine. As a result, vibration of a vehicle is increased, and in an extreme case, the device cannot endure the resonance.
As a third point, if a coil spring constituting a part of a damping mechanism is engaged with a flat member of a driving member or a driven plate of a driven member with insufficient gap in the circumferential direction therebetween, mutual rotation between the driving plate and the driven plate will be determined only by a compression degree of the coil spring. As a result, the obtained rotational displacement is insufficient for effecting the dampening or absorbing of vibration and resonance.